Particle simulation of plasmas, employed since the 1960s, provides a self-consistent, fully kinetic representation of general plasmas. Early incarnations looked for fundamental plasma effects in one-dimensional systems with ∼102–103 particles in periodic electrostatic systems on computers with ≲100 kB memory. Recent advances model boundary conditions, such as external circuits to wave launchers, collisions and effects of particle–surface impact, all in fully relativistic three-dimensional electromagnetic systems using ∼106–1010 particles on massively parallel computers. While particle codes still enjoy prominance in a number of basic physics areas, they are now often used for engineering devices as well.